Although it is now well established that collaborative, chronic disease management approaches are clinically and cost effective for treating depression in primary care, we know very little about how such models perform for anxiety disorders, which occur more commonly than depression in primary care and are particularly difficult to manage. To address this gap, we propose the first large-scale effectiveness study to test a collaborative care approach to treating primary care anxiety. This work builds directly on our Collaborative Care for Panic study, key informant interviews of clinicians, patients and clinic administrators, and more recent studies in primary care depression. Based on these considerations, we have developed a single, specially designed intervention called CALM (Coordinated Anxiety Learning and Management), that can deliver evidence-based treatment to patients with any of four anxiety disorders prevalent in primary care (Panic Disorder [PD], Generalized Anxiety Disorder [GAD], Social Anxiety Disorder [SAD], and Posttraumatic Stress Disorder [PTSD]), including those patients with comorbid depression and/or moderate substance abuse. This intervention allows patients treatment choice (CBT and/or medication), uses techniques to maximize patient engagement, and includes stepped care algorithms - approaches successfully employed in large-scale studies of primary care depression. We have also included an ethnically diverse study population, as well as Spanish-speaking patients, and propose qualitative studies to better understand how CALM should be tailored to individual clinics and to examine the acceptability of CALM for disadvantaged patients. These qualitative studies will provide valuable information needed for future dissemination of this approach. The primary aims are: (1) to use experimental, quantitative methods to determine the clinical effectiveness of CALM compared to treatment as usual (TAD) for the above four anxiety disorders (as a group and individually) and to compare CALM and TAU in terms of intermediate outcomes such as quality of care, self-efficacy, and social stigma;and (2) to use qualitative methods to assess acceptability and barriers to sustainability of CALM in participating clinics, providers, and patients. The secondary aims are: (1) to use quasi-experimental methods (e.g. instrumental variables) to examine the effects of appropriate treatment, independent of intervention assignment, on functioning and other clinical outcomes;and (2) to estimate health care costs and cost effectiveness of CALM.